Liberals believe in the idea of constitutionalism because it is seen as the only way in which individual freedom can be defended against the actions of the state.

Liberals believe in the idea of constitutionalism (the practice of limited government brought about by the existence of limited government) because it is seen as the only way in which individual freedom can be defended against the actions of the state.

Liberals see humans as self-seeking creatures who, if they have the power, will naturally use it for their own benefit and at the expense of others. Thus, for liberals, egoism plus power equals corruption, and the statement of Lord Acton, ‘power corrupts and absolute power corrupts absolutely’ rings true. In this sense, all governments are potential tyrannies against the individual and so pose a constant threat to individual liberty. Constitutionalism offers the prospect of limiting the effects of such behaviour. The introduction of external (usually legal) constraints is able to do this. This can be done through a written constitution, which codifies the major powers and responsibilities of government institutions within a single document. A notable example is the US constitution. A bill of rights may also exist. This entrenches individual rights by providing a legal definition of the relationship between the individual and the state. In the absence of a written constitution and bill of rights, such as in the UK, the importance of statute law has been stressed, through the rule of law. Such a concept was also stressed in 19th century Germany through the concept of the Rechtsstaat (a state ruled by law). Therefore, external constraints have been advocated by liberals because they prevent self-seeking individuals from abusing individual freedom.

Liberals have also advocated internal constraints. This is done to prevent the development of absolute power and therefore absolute corruption. Internal constraints disperse political power among a number of institutions and thus creates a network of ‘checks and balances’. This leads to the separation of powers doctrine, which seeks to prevent any individual or small group from gaining dictatorial power by controlling the legislative, executive and judicial functions of government. Such a thing can be seen in the US Presidential system, where the presidency, Congress and Supreme Court are all separated. Because the judiciary reviews the powers of government itself it is especially important that it enjoys formal independence and political neutrality if it is to protect the individual from the state. Other ways of building in internal checks and balances include: cabinet government (checks the Prime Minister); parliamentary government (checks the executive); bicameralism (checks the legislative chamber); federalism (checks central government). Therefore, liberals support internal constraints because they prevent the concentration of power in the hands of a single person or group.